[Clinical significance of Staphylococcus aureus in urine]

Abstract

Introduction: To evaluate the clinical significance of the isolation of Staphylococcus aureus in urine samples.

Methods: A retrospective study was performed on adult patients identified from a microbiology database in a 200-bed general hospital between the years 2000 and 2009. The demographic data, comorbidities, and risk factors, were reviewed, particularly those associated with the concomitant isolation of S.aureus in blood cultures.

Results: The frequency of S.aureus found in urine samples was 0.63%. A total of 43 patients (mean age 68.7 years [SD±16], and 58.1% males) were identified in the database. A Charlson comorbidity index >3 was observed in 20.9%. Concurrent bacteremia was seen in 48.8%. Two groups of patients were distinguished: with concomitant bacteremia (n=21) or without (n=22). Intervention in the urinary tract significantly predicted (P=.00004) bacteriuria without bacteremia (81.8%), compared to bacteremia cases (19%). The attributable mortality was 47.6% in patients with bacteremia compared to non-bacteremia (no deaths), even though the appropriate antibiotic treatment was more frequent among patients with bacteremia (92% and 60%, respectively).

Conclusion: The presence of S.aureus in urine was accompanied by bacteremia in half of the cases, but in patients without previous urinary tract intervention such a possibility increased to 81%. Concomitant bacteremia predicts a worse prognosis even with appropriate treatment.